Two broad classes of band saws are widely used in industry for metal cutting. One type can be described as a horizontal band saw, such as is shown in my U.S. Pat. No. 3,682,030. The second type is the vertical band saw, that is, a saw having a generally vertically oriented band saw carrying frame. In some vertical band saws, the work piece being cut must be advanced past the stretch or cutting portion of the saw blade, for example, in U.S. Pat. No. 2,601,095. In vertical band saws designed for heavier and more precise work, however, the saw blade carrying drive and idler wheels are mounted on a frame which is supported on a movable carriage so that the work piece is held in a stationary or fixed position and the vertically oriented saw blade is horizontally advanced through the work piece from one side to the other.
Typically such vertical band saws are constructed with a carriage which is supported from the stationary base of the band saw by means of a plurality of roller bearings mounted in tracks or channels on opposite sides and underneath the work piece supporting cutting table. Thus, prior art vertical band saws have included a carriage structure which extends outwardly of both sides of the saw blade and usually to a position even with or in advance of the saw blade. Rollers are mounted to the carriage and support the saw blade assembly for horizontal movement in tracks or channels in the saw base. The band saw is also further provided with a hydraulic or pneumatic cylinder which controls the horizontal advancement of the carriage.
While prior art vertical saws have been found to be highly advantageous for many applications, they have also been found to have a common problem, namely, the ability of cutting chips and other debris to become lodged or deposited in the carriage guiding tracks of the saw base. Band saw cutting operations, particularly those which are automated by feed tables and the like, are inherently relatively contaminated environments. Thus, chips, cutting oil, dirt, and other debris are commonly dispersed or showered over the saw cutting table and frame. While most of these materials are caught and collected by chip pans and the like, invariably some of these contaminants are not so collected and become lodged in the carriage guiding tracks. Such debris can impede the smooth and uniform stroke or horizontal movement of the saw blade carriage. The result can be inaccurate cuts produced by saw blade misalignments and varying cutting pressures.
Another source of inaccurate band saw cutting is the band saw feed table. It is a well known and highly desirable practice to employ automatic feed tables to feed bar stock or the like to vertical band saws and other machine tools. Typically, such feed tables include at least one movable vise which is formed to grip the work piece, move toward the machine tool until a stop is reached, hold the work piece until it is cut, release the work piece and move away from the machine tool to re-grip the work piece and repeat the cycle. While such automatic feed tables have many advantages, it is also well known that they can introduce problems which result in inaccurate cutting, for example, misalignment and an inability to cut to the proper length. Some of the problems which have heretofore been solved with such automatic feed tables are described in my prior U.S. Pat. No. 3,504,585. As is noted in my prior patent, it is highly desirable for a feed table vise to be able to shift horizontally in a direction laterally of the work piece to accommodate slight misalignments and bends which may exist in the bar stock. While my prior patent discloses a movable vise in which this problem is eliminated, I have also encountered a tendency for the movable vise in such automatic feed tables to tilt about a horizontal axis transverse to the work piece. Thus, when the vise grips the work piece and advances the same toward the machine tool until it reaches a stop, there is some tendency for the vise to tilt in its viseways backwardly or away from the machine tool. This tilting action can cause the saw to cut the work piece inaccurately. Correction of this problem should not be accomplished at the sacrifice of the necessary lateral freedom of the vise.
Another source of cutting inaccuracy similar to backward tilting of the vise can be produced when the piece of stock is slightly bent or warped about a horizontal axis so that it is bowed up or down as supported on the feed table. Such bending or misalignment of the work piece can produce extremely high load concentrations on the roller support assemblies of the feed table. Thus, a bent work piece can be severely enough misaligned so that substantially the entire weight of the work piece will be concentrated on a single roller assembly. Such concentrated support can cause several problems including rapid fatiguing of the roller assembly and pivoting of the work piece on the roller assembly so as to tilt the same at the area in which the cut is occurring. The feed table roller supports, therefore, should additionally compensate for unusual load concentrations as a result of work piece bowing or misalignment in a vertical direction.
A final source of cutting inaccuracy which is commonly encountered in connection with band saws has been the cutting and inaccuracy produced by saw blade guide assemblies. Conventional guide blade assemblies, such as is disclosed in my United States Patent No. 3,848,493, employ extremely high strength saw blade engaging guide elements or pads, usually formed of tungsten carbide or the like. These high strength, hard guide blade elements engage the sides and back of the blade and often are required to twist the blade by 90.degree. to provide a cutting stretch which is properly oriented. Such carbide saw blade guides are quite adequate and satisfactory in their operation as long as they are properly lubricated. It is not uncommon, however, for saw operators to be somewhat inattentive with regard to blade lubrication. Accordingly, metal particles being sawed are sometimes driven along the saw blade and between the blade and the extremely hard carbide guides. When the lubrication is not adequate, the chips and particles begin to abrade the blade, reducing blade life and cutting accuracy. It is quite common, therefore, for band saw blades which are guided by carbide saw blade guides to become scored, pitted or dull as a result of inadequate lubrication and passage of chips between the very hard carbide guides and the softer steel blade.
Accordingly, it is an object of the present invention to provide a vertical band saw having a carriage which is mounted for guided movement in a manner enhancing cutting accuracy and reliability.
Another object of the present invention is to provide a vertical band saw having a movable carriage which is less susceptible to interference in the operation thereof from chips and other contaminants.
Still another object of the present invention is to provide a vertical band saw having a movable carriage which is extremely durable, affords improved cutting accuracy, and is inexpensive and relatively easy to manufacture.
Still a further object of the present invention is to provide an automatic feed table for a vertical band saw or other machine tool in which a movable vise is stabilized against backward tilting to enhance the accuracy of the machine tool operation.
Another object of the present invention is to provide a stabilizing means for a movable vise on an automatic feed table which can be easily and quickly attached or installed to existing equipment.
Still a further object of the present invention is to provide a stabilizing device for a movable vise on an automatic feed table which is simple in construction, highly durable and does not interfere with lateral vise freedom.
An additional object of the present invention is to provide a roller support assembly for use on a feed table for a vertical band saw or other machine tool which can accommodate load concentrations induced by work pieces which are warped or misaligned about a horizontal axis.
Another object of the present invention is to provide a roller support assembly for a feed table which has improved resistance to fatiguing.
Another object of the present invention is to provide saw blade guide means which greatly enhances saw blade life.
Still a further object of the present invention is to provide saw blade guide means which are constructed in a manner producing improved cutting accuracy and which are less susceptible to lubrication failures.
The present invention has other objects and features of advantage which will become apparent from the accompanying drawing and are set out in more detail hereinafter.